Engine warming apparatus



March 25, 1947. A. w. RUFF 2,418,097

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ENGINE WARMING APPARATUS Filed Feb. 24, 1943 4 Sheets-Sheet 2 S a l,

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ENGINE WARMING APPARATUS Filed Feb. 24, 1945 4 Sheets-Sheet 3 265V 7 y cca 1 103 7 Ac r II \I\ DC,

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March 25, 1947..

A. w. RUFF 2,418,097

ENGINE WARMING APPARATUS Filed Feb. 24, 1943 4 Sheets-Sheet 4 00000 oozozozozozoo 90.0000

Patented Mar. 25, 1947 ENGINE WARMING APPARATUS Alonzo W. Ruff, York, Pa., assignnr to York- Shipley, Inc., York, Pa., a corporation of Delaware Application February 24, 1943, Serial No. 476,974

14 Claims. 1

This invention relates to engine warming apparatus, and more particularly to a direct firedheater for Warming an airplane engine by discharging a blast of hot gases including products of combustion into the engine housing, cowling, or nacelle. In a preferred embodiment, the heater is adapted for detachable mounting on the engine housing and is connected with the interior thereof by a short length of tubing or pipe.

The art of aeronautics has long been confronted with the problem of starting airplane engines without their being damaged or subjected to excessive wear for want of proper lubrication. This problem is usually presented where airplanes are located in a cold or frigid region or atmosphere. An airplane may not safely begin a flight except as its engine or engines are Warm and at a temperature which is efficient for flying operations. Nor may an airplane engine be started while cold without incurring the risk of its being injured for lack of adequate lubrication. It has, however, been a common practice in preparing airplanes for flight to start their engines while cold and to have them operate until their temperature has reached a degree which is efficient and safe for flying. This practice is time consuming, wasteful of engine fuel, and may result in damage to the engines. In a cold engine,'lubricant is thick, is slow in circulating t and between surfaces requiring lubrication, and is ineffective to prevent Wear of moving parts and surfaces engaged thereby.

Where aircraft are exposed to the elements in an extremely cold environment, region, or atmosphere, it is most diflicult, if not impossible, to start their engines for the purpose of warming them for flight.

The present invention solves the described problem of the aircraft art and provides a heater which, in any natural environment, will quickly warm an aircraft engine to an efficient starting and operating temperature. With the use of this heater, an airplane, regardless of ambient temperature or the degree of cold of the surrounding atmosphere, may have its engine heated and be prepared for flight in a remarkably short interval of time. The heater operation is sensitive and responsive to the temperature of the surrounding atmosphere, its firing rate automatically increasing with decreasing ambient temperature. Accordingly, in colder atmospheres the heat output of the heater is greater and satisfies a greater demand. Under warmer atmospheric conditions, the firing rate and heat l 2 output are less and overheating of the heater is avoided.

The light weight, compactness, and high heat output of the portable heater make it particularly well adapted for use as regular flying equipment of aircraft. The heater may be conveniently stored in the aircraft fuselage, conveniently carried in one hand by a crew member, and readily mounted on the engine nacelle for use in warming the engine wherever the aircraft may be grounded. As part of the flying equipment of a seaplane, the heater may be used by a crew member in warming the seaplane engine while the seaplane is floating on sea or ocean and without the crew member leaving the seaplane.

It is, therefore, an object of this invention to provide a heater which in a highly eflicient operation, is adapted to warm quickly an airplane engine to an efficient starting and operating temperature.

A further object is to provide an efficient, lightweight, compact, portable engine warming heater which may be conveniently, detachably, and quickly mounted on an airplane engine housing, cowling, or nacelle.

Still another object is to provide a relatively small and lightweight portable airplane engine warming heater which is characterized by its high heat output per unit of heater weight. Thus the heater of this invention has remarkable efliciency as regards heat output per unit of heater weight. I

A still further object is to provide a portable airplane engine warming heater which is selfcontained except for a source of electrical current and which may derive its electrical current from an available source carried by the airplane, the connection between the source and heater being made with a power cable.

Usually the current available on an airplane is direct current. The invention, therefore, has for a further object the provision of means in the portable heater for changing available, low voltage direct current to high voltage current for an electrical spark fuel igniter of the heater.

Still another object is to provide a portable engine warmer with combustion and heating means of novel construction to secure maximum heat energy per unit of fuel consumed in operation of the engine warmer.

A still further object is to provide an aircraft engine warmer having a firing rate responsive to ambient temperature. 7

Another object is to provide a novel mounting 3 for supporting an engine warmer on an aircraft engine nacelle, cowling orhousing.

Other objects and advantages will be apparent from the following description, the appended claims, and the accompanying drawings, wherein Figure 1 is a side elevational view of the front end of an airplane nacelle equipped with a heater of the present invention.

Figure 2 is a rear view on enlarged scale taken on line 2-2 of Figure 1 and with the closure of the burner nozzle compartment removed for purposes of illustration.

Figure 3 is an enlarged elevational view of the heater of Figure 1 with the closure of the motor, fan, and compressor compartment in open position for purposes of illustration.

Figure 4 is, in general, a diagrammatic view of the elements of the heater of Figures 1 to 3 and its wiring. For purposes of illustration, the combustion and heating unit of the heater is shown in longitudinal cross-section in Figure 4.

Figure 5 is a detail view in cross-section, being taken on line 5-5 of Figure 2- and showing the nozzle compartment closure.

Figure 6 is a detail view in cross-section and taken on line 6-6 of Figure 3.

Figure 7 is a front end view on enlarged scale of the heater of Figure 1, the hose and its coupling member being removed in Figure 7 for purposes of illustration.

Figures 8 and 9 are enlarged detail views in cross-section showin the safety air valve of the heater in two positions of adjustment.

Referring now to the drawings, the heater of this invention comprises a compact arrangement of an air warming and combustion assembly or unit A, a fuel tank unit B, a motor, fan and compressor assembly or unit 0 for supplying air to the unit A, pipe and electrical connections for the units A, B and C, and a hose or pipe D through which the hot gases of the unit A pass for introduction into the nacelle or engine housing of an airplane.

The heater has a housing including front and rear wall members l6 and I (Figures 7 and 2). The side walls and bottom of the housing are formed by a sheet-like member l2 and a closure l3. The member I2 is secured at its longitudinal edge H in any suitable manner to the adjacent sidewall of the combustion and heatin assembly A (see Figures 2 and 7). cured by means of hinges to the other longitudinal edge of the member l2 and is retained in closed position by latching devices I6 which are mounted on the side of the combustion unit A.

- When the closure I3 is in open position (Figure 3),

the interior of a motor, fan, and compressor compartment is conveniently accessible.

The heater is of such weight and size that it may be conveniently carried by an individual. A handle ll in the form of a strap secured to the top wall of the combustion unit A permits the heater to be carried in the hand in substantially 'the same manner as a traveling bag.

As shown in Figure 1, the heater of this invention may be readily mounted on the housing or nacelle 2| of an airplane engine by means of a saddle or support 22 and a strap or belt 23 having a conventional buckle 24. The saddle 22 is shaped to fit the engaged part of the engine housing 2| and has inwardly facing flanges 26 at its forward and rearward edges to form guideways. The saddle 22 is held firmly in place by the strap 23 which extends over the saddle 22 and completely encircles the engine housing 2|. The base of the The closure I3 is seheater has forward and rearward flanges 21 which interfit with the saddle flanges 26 and the guideways formed thereby (see Figure 3). The saddle 22 having been secured to the engine housing 2|, the heater is mounted in place on the saddle 22 by a side-wise movement with the heater flanges 21 sliding in and retained by the saddle guideways. The discharge end of the hose D is then positioned to direct the hot gases of the heater into the interior of the engine housing 2| (Figure 1) for warming the engine therein when the heater is operating. The entrance of cold air into the open front end of the engine housing 2| is prevented, during the prewarming operation, by a removable shield 28 of any suitable form, such, e. g. as a heavy canvas covering.

Combustion and heating unit The combustion and heating assembly or unit A is fed with fuel from the fuel tank unit B and with air from the motor, fan and compressor unit 0. The air supplied by the unit C to the unit A performs a number of functions. 'It provides primary air for the unit A, draws the fuel from the unit C by suction, and sprays the fuel into the unit A where the fuel is burned. It also provides secondary air to the fuel burning in unit A. It, furthermore, supplies air for absorbing heat lost in the unit A by the products of combustion. All the gases in the unit A, that is the products of combustion and the air heated thereby, are discharged into the hose D and serve to warm the airplane engine.

The combustion and heating unit A includes a tubular member 3| which serves as both an air duct and as a housing for a fuel burner 39 and a firing tube 33. For convenience, the member 3| will hereinafter be referred to as 'a duct or an air duct. The front end of the duct 3| i provided with a'removable fitting or coupling 34 for connection with the hose D (see Figure 3). The rear end of the duct 3| houses the burner 39 and is provided with a removable closure 36, as shown in Figures 3 and 5. For the purpose of illustration, the heater is shown in Figure 2 with the closure 36 removed and in Figure 7 with the fitting 34 removed.

' A partition or wall member 31 separates the burner compartment from the remainder of the duct 3| and is provided with an annular series of pressure equalizing openings 38 (see Figures 2 and 5).

The burner compartment (see Figures 2 and 5) contains the aspirating fuel burner nozzle 39 and a fuel igniting spark electrode 4|. The nozzle 39 and the electrode 4| are carried by brackets 42 and 43 respectively which are mounted on the partition 31. The partition 31 also has a central opening at which a fitting 44 is mounted. This fitting 44 has an aperture 46 aligned with the nozzle 39.

Air under pressure is fed by a pipe 41 to the aspirating nozzle 39. This primary air draws fuel into the nozzle 39 from a pipe 48 by suction (Figure 5), the air and fuel issuing from the nozzle 39 as a fluid spray. This spray is ignited by an electric are or spark which is formed between the tip of the spark electrode 4| and the fitting 44. The ignited spray is directed through the aperture 46, the fitting 44 and the central opening of the partition 31. The ignited fuel and air mixture or spray then passes through an opening 55 defined by an annular air register and into the fire or combustion tube 33.

The air register provides secondary air, which is so introduced into the spray from the nozzle 39 as to be thoroughly mixed therewith and to impart a whirl to the ignited fuel spray. This air register (Figures 4, 5 and 6) i formed by an annular partition member 53, a centrally apertured wall member 5|, the centrally apertured partition 31 and an annular series of stationary vanes 52. The annular partition member 50 encircles the firing tube 33 and is secured to the inner end flange thereof. The wall member 5| is' spaced from the partition 31 by the vanes 52 and has a central opening 53 (Figure 5) which is of the same size, and aligned with, the central opening in the partition 31. Air flows into the air register at the periphery thereof, and along passages 54 which are formed by the wall member 5|, the vanes 52 and the partition 31. .The air register passages 54 discharge the secondary air into the sp age or opening 55 having its limits defined by the inner edges of the vanes 52. This secondary air discharge is substantially tangential to the fuel spray from the burner nozzle 33. Thu the secondary air is discharged with a whirl imparted thereto which surrounds the path of the nozzle spray. This whirling secondary air supply issuing from a series of passages completely encircles the fuel spray and its whirl component isimparted to the fuel spray. The force of the fuel spray and the secondary air from the passages 54 is effective to produce continuous discharge of whirling gases through the space or register opening 55 into the fire or combustion tube 33.

The firing tube 33 is constructed to promote complete combustion therein and also to confine the fiame of the burning fuel. Intermediate its ends the firing tube 33 is provided with a ballle 56 (Figures 3 and 4). This bafile 56, which may be in the form of a ring (or a centrally apertured plate, retards the fiow of gases to such extent that combustion is primarily in the fire tube space between the wall member 5| and the baflle 56. The burning gases and air pass the baiile 56 by flowing through its centrally arranged aperture or opening' The firing tube 33 is also provided with two spaced sets (58 and 53) of vanes between its discharge end and the baflle 56. These vane sets 58 and 59 serve as gas mix ing bailles to produce turbulence in the gases passing therethrough. This turbulence brings unburned air into more intimate relation with burning fuel to thereby complete combustion within the firing tube 33 and avoid the possibility of any flame passing through the discharge end 60 of the firing tube. In a preferred form, the vanes of each set 58 and 59 are arranged in an annular eries with the vanes of one set having a pitch opposite to the pitch of the other set. The first vane set 58, therefore, will effect a whirling action in one direction of the gases flowing therethrough, and the second vane set 53 will impart to the gases flowing therethrough a whirling action in the opposite or reverse direction. The retarding effect of the baflle 55 and the whirling effect of the vane sets 58 and 59 result in the fuel being substantially completely burned before the gases or products of combustion are discharged from the firing tube 33.

The firing tube 33 is insulated from the atmosphere by an envelope of air which flows in the space between the fire tube 33 and the housing or duct 3 Air is supplied to the duct 3| through the opening 5|, a portion of which is opposite the described air register. Part of this air flowing through the duct opening 6| travels in an an- 6 nular' path defined by the duct 3|, the partition members 31 and II, and the end edges of the air vanes 52 and through the series of air register passages 54, as previously described, to provide secondary air for the firing tube 33. A limited volume of air travels through the openings 38 to equalize the pressures at opposite sides of the partition 31. The remainder of the air from duct opening 3| fiows through the annular space between the duct 3| and the firing tube 33 and then through the discharge opening 62 (Figure 4) of the duct 3i. This flowing air in the duct 3| absorbs heat that is conducted through the walls of the firing tube 33, and moves quickly to the duct,discharge 32 with the result that little, if any, heat is lost by conduction through the walls of the duct 3| to the atmosphere. Loss of heat to the atmosphere is further avoided by means of a heat shield 63 in the form of a tubeor sleeve. The heat shield 63 extends from adjacent the duct opening 6| to adjacent the dis charge end of the firing tube 33. The shield 63. the duct 3|, and the firing tube 33 are concentrically arranged in spaced relation to provide inner and outer annular air passages 64 and 65 respectively. The air flowing in passage 64 absorbs a major part of the .heat passing through the walls of the firing tube 33. The air flowing in passage 65 acts as an insulating medium and is effective to maintain the duct 3| in a relatively cool condition. The products of combustion flowing from the discharge end of the firing tube 33 mix with the warmed or hot air flowing from the annular passages 54 and 65 as shown in Figure 4. This hot gaseous mixture of warmed air and products of combustion flows through the hose D and into the engine housing or nacelle 2 The duct 3|, the firing tube 33, and the heat shield or sleeve 63 are secured in assembled relation by means of brackets or spacers 68 and 61 (see Figures 3 and 7).

The hose D is flexible and alsoaxially collapsible. The collapsible feature permits the hose D to be compactly arranged for storage when not in use. During storage of the heater, the hose D may be detached by removal of the fitting34 from the duct 3|. The hose D is preferably formed by a flexible asbestos tube supported internally by a plurality of spaced rings or, by a coiled wire or spring. The hose D insulates the gases flowing therein from the atmosphere and thereby minimizes heat loss. Waste of heat is further avoided by mounting the heater on the engine housing and in close proximity to the point of'discharge into the engine housing interior. Thus the blast of hot gases from the heater has a relatively short path of travel before reaching the engine to be warmed.

Fuel tank unit The portable engine warmer or heater includes a tank 1| (Figures 2 and 7) for holding a supply of fuel, which preferably is gasoline. The tank H is arranged at a lower level than the fuel nozzle 39 and is connected thereto by the fuel supplypipe line 48, which is fitted with a manually controlled valve 12 for cutting off the fuel supply to the nozzle 35 when such is desired. The valve fitting 12 preferably includes a strainer or filter (not shown) in the fuel line in order to prevent passage of any solid matter or sediment to the burner nozzle. Fuel may be supplied to the tank 1| through a fill pipe 13 having a closure or cap 74. The fuel tank 7| preferably is of circular cross-sectional shape of a length and diameter corresponding to that of the duct 3|. As I cured by providing the, tank II and the heating and combustion unit A in close, parallel relation with the tank II corresponding in shape and size to the unit A. e

' Motor, fan and compressor "flit The heater has an electric motor I8 driving both an air fan 11 and an air compressor 18,

which are operated directly by the motor shaft I9 (see Figures 3 and 4). The shell or casing of the air compressor I8 is supported by the housing of the motor 16, which is secured to the duct 3I by means of a bracket or angle iron 88.

The discharge of the air compressor I9 is fed by the pipeline 41 to the burner nozzle 39 for aspirating fuel from the tank II and blowing it out of the nozzle 39. The air pipeline 41 may be provided with a pressure gauge 49 which is conveniently positioned to be read from without the heater. A

The air pipeline 4! is also preferably provided with an air safety valve 8I (Figures 2, 8 and 9). The air safety valve 8| comprises a tubular body 82 having a movable ball 83 positioned between a retainer pin 84 and a seat or flange 86. A piston 81 is fitted in the valve body 8| to be moved transversely of the axis of the ball seat 86. The

'piston 81 is operable by means of two pins 88 and 89. The pin 88 is operable to force the piston 81 inwardly to an extreme position, which frees the ball 83 for engagement with the seat 86 to stop th flow of air through the body 82. A compression spring 8|, which is interposed between the pin 88 and the piston '8'I, yieldingly maintains the piston 81 in its projected or ball releasing position (Figure 8). In starting the heater, the pin 89 is pressed inwardly to move the piston 81 to ball unseating position (Figure 9), in which the piston flange 82 engages'the ball 83 and holds it out of engagement with the seat 88. Air under pressure now may flow through th body 82 and will act to hold the piston 81 in its ball releasing position (Figure 9). When the air pressure fails or falls below a predetermined amount, the piston 81 moves, under the action of th spring ill, to release the ball 83 for engagement with the seat 88 (Figure 8) in a valve closing operation. Thus the feeding of fuel is discontinued by an automatic closing operation of the air valve 8| when the air pressure or the compressor I8 fails.

The fan II (Figures 2, 3, 4 and 6) is positioned within a housing 98 having oppositely arranged air intake openings 91 (Figur 4). The air is discharged from the fan housing 98through an outlet opening 98, and the duct opening SI (Figures 2 and 6). The air passing through the duct opening 6| flows along two separate paths in the duct 3| as previously described. One path is through the air register and the firing tube 33. The other path is between the firing tube 33 and the duct 3 I.

Current supply and control The electrical current for operating the heater is provided by a power cable I8I which is adapted for detachable connection .with an available source (not shown), such as a battery or generator, within the airplane fuselage. The heater is wired and electrically controlled as diagrammatically illustrated in Figure 4. The heater controls include a starting switch I82, 9. safety overload switch or aviation relay I83, and a the!- mostatic device Orautomatic limit switch I94. The switch I82 is manually controlled for start-' ing the motor I8. This switch I82 may be of the type which is closed by the operator and released by the operator when the unit has established normal operation and the limit switch has taken its operating position. The thermostatic device I84 has a temperature responsive element I88 extending into the air stream of the duct 3| asshown inFigures 3, 4 and 7. This thermostatic devic I84, operating through the relay I93, opens the motor circuit when the air stream of the duct 3| reaches a predetermined maximum temperature, or a predetermined minimum temperature. Thus, overheating is prevented, and

at the same time, the thermostatic device I94 will open the motor circuit, after operation of the burner has been initiated, in event of subsequent failure of fuel, flame, or combustion.

The motor I6 is supplied with DC. current by the wiring I86 (see Figure 4) and as illustrated is provided with a slip ring and brush assembly I8l to supply A. 0. current for the burner spark electrode 4|. A transformer I88 provides the desired voltage for the spark electrode 4i. Alternatively an interrupted or pulsating unidirectional current may be used for ignition purposes.

In this case, a rotary make and break switch on the motor shaft may be used, by which the D. C. supply current from which the motor is operated, to furnish pulsating current to a suitable spark coil (not shown) in lieu of the transformer I98. As shown in the drawing the ignition circuit is closed, at starting, by closing the switch I82, and it is intended that the supply of ignition current will be interrupted (cut-off) when normal operation of the burner has been established, at which time the switch I82 is permitted to move to its open circuit position.

The starting switch I82 is mounted on the rear end wall II (Figure 2). The overload relay I93, the thermostatic switch I84, and the transformer I88 are mounted within one end of the motor,

fan and compressor compartment as shown in Figures 3 and 7, and are easily accessible for inspection or repair when the closure I3 is opened. During operation of the motor 18, the fan 'I'I creates a draft of air through the interior of the heater. The air is drawn into th heater through the front wall opening, which is provided with a screen III (Figure 7). Air passing through this screen III sweeps the exposed surfaces of the overload relay I83, the limit switch I84, the transformer I88, the fuel tank II, the duct 3|, the compressor I8, and the motor I8. Thus the air absorbs heat from warmed surfaces. The air thereby maintains the contacted heater parts at a cool temperature for efllcient operation, Th air also minimizes heat loss from the duct 3|, and at the same time maintains the fuel tank II at a cool temperature to avoid any possibility of fire or explosion due tooverheating of theffuel tank II. Air drawn through the front wall screen III travels to the other end of the heater where the air enters the fan casbrication for the compressor II is supplied from a reservoir I I2 (Figure 3).

Operation 7 The heater is mounted in the following manner for warming an airplane engine. The saddle 22 and the strap 23 are secured in position (Figure 1) on the engine housing, cowllng, or nacelle 2!. The front of the engine housing II is covered with a shield or hood 28. The heater is mounted (Figure 1) in the saddle 22 and has the discharge end of its hose D positioned to extend through a suitable opening in the hood 28. The power cable I of the heater is connected to the source of current (D. C.) on the airplane.

The heater operation is initiated by opening the fuel supply valve 12, closing the motor starting switch I02, and operating the air valve pin 89 to open the air safety valve II. Actuation of the switch I02 closes the motor circuit to start the motor I6, which latter by generator action provides current for the fuel igniter electrode M and also drives the air compressor 18 and the air fan 11. The fuel igniting spark from the electrode 4i may be checked and inspected at this time by viewing the same through a peep hole IIG (Figure 5) in the top wall of the duct 3|. The pressure of the air supplied by the compressor I8 may be checked by inspection of the gauge I9 (Figure 2).

Air from the compressor 13 flows through the pipeline 4! to the aspirating, burner nozzle39 and draws fuel through the pipeline 48 from the fuel tank II. This air also mixes with the fuel in the nozzle 39 and produces a nozzle discharge in the form of a gaseous spray of fuel and primary air for combustion. This spray is ignited by the spark from the electrode ll and is directed through the air register space 55 into the firing tube 33.

Air from the fan I1 is discharged through the outlet 98 into the duct 3| to provide secondary air for the air register passages 5| and also an air stream through the space between the firing tube 33 and the duct 3I. The secondary air is discharged by the air register passages 54 into the air register space 55 where the secondary air mixes with and imparts its whirl to the ignited spray from the burner nozzle 39. The resulting whirling gaseous mixture flows into the interior or combustion space of thefiring tube 33. Combustion of the burning gases issuing from the air register space 55 is completed in the firing tube 33 where it is confined with the aid of the baffle 56 and the vane sets 53 and 59. The baflie 56 retards the movement of the burning gases along the firing tube 33. The gases pass the baffle 56 by passing through its central opening. The vane sets 58 and 59 are efiective to impart to the burning gases successive whirling movements in two opposite directions and thereby $0 mix the gases passing therethrough that combustion is completed before they leave the firing tube 33.

Part of the air from the fan II. as previously noted, flows through the space between the firing tube 33 and the duct 3I including the passages 64 and 65 (Figure 4). This air insulates the firing tube 33 from the atmosphere and also is warmed by heat passing through the firing tube walls. The warmed air from the passages Iil and 85 is discharged into the duct outlet 62 and at the same time is mixed with the products of combustion flowing through the outlet of the firing tube 33. This mixture of hot gases flows through the hose D into the engine housing 2| and, in a remarkably short interval of time, warms the engine therein to a desired starting temperature.

In the event the temperature of the air stream surrounding the outer end of the firing tube33 I compressor I8 stops operating, and the pressure in the air pipeline 41 fails. The safety valve 8| (Figures 8 and 9) then automatically closes the air pipeline 41.

Atmospheric air enters the heater through the front wall opening having the screen III and flows through the interior of the heater over the motor and compressor, to the intake of the compressor 18, and to the inner intake 91 of the fan housing 96. This air fiow also cools the fuel tank II, the transformer I08, the overload relay I03, the switch of the thermostatic device I04, the compressor I8, and the motor I6. This air fiow also minimizes heat loss from the duct 31 to the atmosphere. The fan 1'! draws air directly from the atmosphere through the fan housing intake opening 91 shown in Figure 2 and also air from the motor, fan, and compressor compartment through the other fan housing intake opening An important characteristic of the heater is its sensitiveness and responsiveness to environment and atmospheric conditions. The heater may thus be used in various climates or under varying ambient temperature conditions with equal success. It is found that the firing rate of the heater and hence its capacity to supply heat increases with lowering of the ambient temperature or of the temperature of the surrounding atmosphere. In other words, the'firing rate varies inversely with the ambient temperature. Increased demand on the heater due to an extremely low temperature is met automatically by an increased firing rate. On the other hand, the danger of overheating is avoided since the firing rate is lower when the heater is used, for example, in

a moderately cold climate. This variation in firing rate with change in ambient temperature is believed to be the result of the use of gasoline as fuel and the use of suction in lifting the fuel from the tank 'II and feeding it to the nozzle 39 by means of air from a compressor or the like. Since density of the air varies inversely with its temperature, the colder the air, the greater its density andinertia effect. With increase in the density and inertia of the air, increased fuel pumping action by the compressed denser air, as well as increased air supplied by the blower, is secured. The tendency of the gasoline tovaporize varies inversely with its temperature. As the temperature of the gasoline is lowered, its tendency to form vapor in the nozzle head decreases with the result that fiow of the gasoline through the nozzle is correspondingly increased.

The increase in fiow of gasoline, due to lowered temperature condition, is also attributable in part to the fact that the density of the gasoline increases somewhat with lowering temperature.

Other important features of the present heater are its high heat output per unit weight, and its auaoev emciency in avoiding heat losses to the atmosphere. A large proportion of the heat of combustion is carried by the products of combustion to the point of use, namely the interior of the engine housing 2|. Substantially all of the heat lost by the products of combustion is absorbed by the air stream from the fan 11, this air stream being mixed with the products of combustion before introduction into the engine housing .2 l The air passing through the interior of the heater to the fan I1 also absorbs any friction heat generated by the mechanical, operating parts of the heater. Accordingly, the heater may have its useful "heat output somewhat in excess of the heat produced by combustion.

The light weight and compactness of the heater contribute to its usefulness. It may be easily carried in the hand and may be conveniently stored in an airplane as part of its regular flight equipment. The heater is especially useful with seaplanes which cruise or fly over the seas and oceans and frequently land on the water far from shore and the equipment which is usually found at shore bases.

The foregoing is to be understood as illustrative, since this invention includes all embodiments and modifications coming within the scope of the appended claims.

I claim:

1. A compact and portable aircraft engine heater comprising a casing having an air inlet,

a motor and fan unit in said casing, an air warmer and combustion unit having outer wall surface exposed to the interior of said casing, a fuel tank having outer wall surface exposed to the interior of said casing, a fuel burner for said air warmer and combustion unit, said fuel burner being supplied with fuel from said tank, said fan drawing air from said casing inlet to produce air circulation through said casing interior and discharging the air into said air warmer and combustion unit, and a pipe for receiving the discharge of heated air and products of combustion from said air warmer and combustion unit and introducing the discharge into an aircraft engine nacelle.

2. A compact and portable aircraft engine heater comprising a, tubular fuel tank adjacent the base of the heater, a motor, fan, and compressor unit extending parallel to and at one side of said tank, an elevated tubular air warmer and combustion unit extending parallel to said tank, and adapted to be supplied with air from said fan, a burner for said unit and adapted to be supplied with fuel in said tank by aspirating air from said compressor, means forming with said tank and said air warmer and combustion unit a protective enclosure for said motor, fan, and combustlon unit, and an outlet pipe for warmed air and products of combustion discharged by said air warmer and combustion unit.

3. A heater as recited in claim 2, wherein the pipe is connected to the air warmer and combustion unit at one end of the heater, and the burner is positioned at the other or rear end of the heater, and controls for the motor, the fuel supply to the burner, and the supply of aspirating air to the burner which are mounted at said rear heater end.

'4. A portable, self-contained, outdoor heater for supplying hot gases to an aircraft engine nacelle to warm the engine in preparation for its starting, the said heater comprising a combustion unit, a fuel burner nozzle and an electric sparking device positioned to ignite the fuel mixture issuing from said nozzle, a fuel tank 12 communicating with said nozzle, a compressor for supplying compressed air and fuel from said tank to aid nozzle, an electric motor for driving said compressor, means deriving its energy from operation of said motor for supplying ignition current to said sparking device, and means for conducting the heated gases from said combustion unit for introduction into the engine nacelle.

5. In a portable heater unit for preheating the engine of an airplane preparatory to its starting, the combination comprising: a housing having side and end walls with an air inlet, and an outlet for the discharge of heated air and products of combustion, a combustion chamber mounted within said housing and spaced therefrom, to provide for air circulation to wipe the outer wall surface of said chamber, a fan for supplying a current of air through said housing from said inlet and along the outer wall surface of said chamber, means for diverting a part of the circulated air into the said combustion chamber to support combustion therein, an atomizing burner nozzle for discharging a mixture of air and fuel into said combustion chamber, a fuel tank within the housing for supplying fuel to the burner, an air compressor also within the housing for supplying air under atomizing pressure to said burner, a motor for operating the said fan and compressor, and means for conducting heated air and the products of combustion from the outlet of said housing to the nacelie of an engine to be heated.

6. A portable heater unit as recited in claim 5, wherein the air diverting means is an air register in the form of an annular series of passages arranged substantially tangentially to the outlet opening into the combustion chamber, the said passages communicating at their outer ends with the housing air inlet and at their inner ends with the combustion chamber.

'7. A portable heater unit as recited in claim 5 wherein the housing and the combustion chamber are concentrically arranged tubular members. and a heat shielding sleeve surrounds the inner tubular member or combustion chamber and is spaced from both of. said tubular members to provide concentric annular passages for air flowing from the housing air inlet to the housins. outlet.

8. A portable engine heater unit as recited in claim 5, wherein the combustion chamber i a tubular member having a baffle intermediate the ends thereof for retarding the fiow of burning gases through the chamber and having means adjacent the discharge end thereof for imparting whirling movements to the hot gases flowing in said chamber to said discharge end, the said baille and last named means serving to prevent flame travel beyond the confines of the combustion chamber.

9. A compact, portable aircraft engine heater for preheating the engine preparatory to its starting, the combination comprising a fuel tank adjacent the base of the heater, a driven shaft extending parallel to said tank and motor means for driving the shaft, a fan and compressor mounted on said shaft and driven thereby, an air warmer and combustion unit elevated above said fuel tank and adapted to be supplied with air from said fan, an atomizing burner for said unit operated by compressed air supplied by said compressor, means for supplying fuel from said tank to said burner. and means for conducting warmed air and products of combustion from said unit into an aircraft engine nacelle.

10. A compact, portable engine heater for preheating the engine preparatory to its starting, the combination comprising; a fuel tank, a driven shaft, a fan and compressor mounted on said shaft and driven thereby, an air warmer and combustion unit adapted to be supplied with air from said fan, a burner for said combustion unit adapted to be supplied with fuel from said tank by pressure of air from said compressor, means for conducting warmed air products of combustion from said unit into an aircraft engine nacelle,

9. housing for enclosing said fuel tank, fan, compressor and combustion unit to contitute a rigid unitary assembly, and means comprising interfitting parts for detachably supportingthe heater upon the exterior of the cowling of the engine to be heated.

11. A compact and portable engine heater comprising; a casing having end, bottom and side walls, a fuel tank adjacent said bottom wall, a motor, fan, and compressor unit extending parallel to and at one side of said tank, a tubular air warmer and combustion unit elevated above said fuel tank and adapted to be supplied with air from said fan, a burner for said unit adapted to be supplied with fuel from said tank by aspirat ing air furnished by the compressor, an outlet pipe for discharging warmed air products of combustion into an aircraft engine nacelle, and means carried by the casing for detachably securing said heater to the engine cowling.

12. In a compact and portable engine heater for preheating the engine preparatory to its starting and adapted to be detachably connected to the engine cowling, the combination comprising; a housing having an air inlet and outlet, a fuel tank in said housing, a fan and compressor unit extending along one side of said tank, an air warmer and combustion unit in said housing adapted to be supplied with air from said fan, a burner for said combustion unit adapted to be supplied with fuel from said tank by air pressure supplied by said compressor, said air warmer and combustion unit including a tubular member having an air register in communication with the air inlet, a bailie spaced from said register for retarding the flow of burning gases discharged therefrom, means adjacent the discharge end of said combustion unit for imparting successive whirling movements in opposite directions to the gases flowing in said tubular member toward the outlet of said casing, a motor to drive 'said fan and compressor, and a pipe for conducting warmed air and products of combustion dis-- charged by said air warmer and combustion unit to the engine nacelle.

13. For use in warming an airplane engine to starting temperature, the combination comprising; a portable, self-contained combustion-type heater, a hose for conductinghot gases from said heater to the interior of the engine cowling, a saddle adapted to be mounted on the engine cowling to support said heater exteriorly of said cowling, guideways on said saddle interfitting with flanges on said heater to provide for mounting and removal of said heater in a sliding operation, and means for securing detachably said saddle to the engine cowling.

14. For use in warming an airplane engine to starting temperature, the combination comprising; a portable, self-contained combustion-type heater, a hose for conducting hot gases from said heater to the interior of the engine cowling, a saddle adapted to be mounted on the engine cowling to support said heater exteriorly of said cowling, and a strap-like member adapted to substantially encircle the engine cowling to secure the saddle in position on the cowling.

ALONZO W. RUFF.

REFERENCES CITED The following references are of record in the file of this patent:

, UNITED STATES PATENTS Number Name Date 1,629,921 Mansfield May 24, 1927 1,677,197 Myers July 17, 1923 2,097,255 Saha Oct. 26, 1937 2,000,733 Avery May 7, 1935 1,423,742 Silverman July 25, 1922 781,308 Smith Jan. 31, 1905 2,066,524 Gehmich Jan. 5, 1937 2,295,177 King Sept. 8, 1942 1 1,862,114 Gilly June 7, 1932 508,689 Engelman Nov. 14, 1893 1,943,053 Boisset Jan. 9, 1934 2,015,982 Witzel Oct. 1, 1935 2,196,828 Hess Apr. 9, 1940 

